He said McCain weren't allowed to sell the (specific) fries to other fast-food clients.

While we thought it might be interesting to share the scale in which McCain operates – it probably supplies hundreds more chain restaurants in Britain, some may even use the supermarket product – we've mentioned McDonald's using its potatoes before.

Last year, we mentioned the process by which McDonald's fries are given their 'unique' flavour: "hydrolysed wheat and hydrolysed milk as starting ingredients."

"Following the blanching process we add a dextrose solution to have that nice even coat that we see in the restaurants," said Mario Dupuis, a production manager for McCain.

"We also add an ingredient to our strips to make sure that we prevent the graying of our product throughout the process."

So if you bought McCain frozen fries, and added sodium acid pyrophosphate (used to maintain the colour), together with hydrogenated soybean oil and salt, you could potentially make McDonald's fries at home.